Debris sensors, including some suitable for cleaning apparatus, are known in the art. Debris sensors can be useful in autonomous cleaning devices like those disclosed in the above-referenced patent applications, and can also be useful in non-autonomous cleaning devices, whether to indicate to the user that a particularly dirty area is being entered, to increase a power setting in response to detection of debris, or to modify some other operational setting.
Examples of debris sensors are disclosed in the following: TABLE-US-00001 De Brey U.S. Pat. No. 3,674,316 De Brey U.S. Pat. No. 3,989,311 De Brey U.S. Pat. No. 4,175,892 Kurz U.S. Pat. No. 4,601,082 Westergren U.S. Pat. No. 4,733,430 Martin U.S. Pat. No. 4,733,431 Harkonen U.S. Pat. No. 4,829,626 Takashima U.S. Pat. No. 5,105,502 Takashima U.S. Pat. No. 5,136,750 Kawakami U.S. Pat. No. 5,163,202 Yang U.S. Pat. No. 5,319,827 Kim U.S. Pat. No. 5,440,216 Gordon U.S. Pat. No. 5,608,944 Imamura U.S. Pat. No. 5,815,884 Imamura U.S. Pat. No. 6,023,814 Kasper U.S. Pat. No. 6,446,302 Gordon U.S. Pat. No. 6,571,422
Among the examples disclosed therein, many such debris sensors are optical in nature, using a light emitter and detector. In typical designs used in, e.g., a vacuum cleaner, the light transmitter and the light receiver of the optical sensor are positioned such that they are exposed into the suction passage or cleaning pathway through which dust flows. During usage of the vacuum cleaner, therefore, dust particles tend to adhere to the exposed surfaces of the light transmitter and the light receiver, through which light is emitted and detected, eventually degrading the performance of the optical sensor.
Accordingly, it would be desirable to provide a debris sensor that is not subject to degradation by accretion of debris.
In addition, debris sensors typical of the prior art are sensitive to a level of built-up debris in a reservoir or cleaning pathway, but not particularly sensitive to instantaneous debris strikes or encounters.
It would therefore be desirable to provide a debris sensor that is capable of instantaneously sensing and responding to debris strikes, and which is immediately responsive to debris on a floor or other surface to be cleaned, with reduced sensitivity to variations in airflow, instantaneous power, or other operational conditions of the cleaning device.
It would be also be useful to provide an autonomous cleaning device having operational modes, patterns of movement or behaviors responsive to detected debris, for example, by steering the device toward “dirtier” areas based on signals generated by a debris sensor.
In addition, it would be desirable to provide a debris sensor that could be used to control, select or vary operational modes of either an autonomous or non-autonomous cleaning apparatus.